Magnetic resonance imaging (MRI) experiments are being conducted at Duke University Medical Center to explore the application of the technique during toxicologic studies. Animals (primarily rats) are anesthetized with a gaseous anesthetic (halothane), given complete and ventilation support, extensively monitored via electronic sensors to determine physiologic status and imaged for variable lengths of time (<1 hour to >4 hours) using a 30 cm bore, 2 Tesla MRI devise. Animals are imaged repeatedly (1 to 4 times a month) during a study. Investigations currently underway include imaging animals that are being treated to develop hepatic neoplasms to determine at what stage the neoplastic process can be detected and if the progression or regression of the tumors can be monitored. Additionally, studies are being conducted to explore the ability of MRI to detect acute renal damage in the rat. During 1988, a 7 Tesla magnetic imaging system will become operational and will provide resolution approximately 10 times greater than that currently available. This will permit the use of MRI in studies using mice in addition to rats. Several scientific articles have been published thus far. These relate to technical developments in small animal imaging, multiple imaging of the rat brain and imaging of the live, developing, chick embryo.